A recent study published in Nature found that the rise of omicron has significantly reduced protection from reinfection with SARS-CoV-2, the pandemic coronavirus. Researchers analyzed population-wide data from Qatar and discovered that COVID-19 infections from pre-omicron variants (such as alpha or delta) offered around 80% protection against reinfection with another pre-omicron variant for over a year. In contrast, omicron provided an initial 80% protection rate within the first six months after infection, but this protection rapidly declined to 27.5% between nine months and a year.
Interestingly, the study found that vaccine efficacy had no bearing on the results of reinfection-derived protection. However, vaccination did not appear to have any significant impact on protection from severe COVID-19 during reinfection, with nearly 100% protection rates observed regardless of the initial strain. The population studied was predominantly male and relatively young, which may limit the generalizability of the findings.
The stark difference in protection between pre- and post-omicron eras highlights the need for continued vaccination efforts to combat periodic waves of infection and protect vulnerable populations. Annual updated vaccines will be crucial in reducing potential disease spikes and minimizing harm during future outbreaks.
Source: https://arstechnica.com/health/2025/02/protection-from-covid-reinfections-plummeted-from-80-to-5-with-omicron